1. Field of the Invention
The present invention relates to a suspension structure for an electric wheelchair, and more particularly to a suspension structure for an electric wheelchair whose mid wheels serving as drive wheels.
2. Description of the Prior Art
An electric wheelchair is usually used by old age or handicapped people for helping them regain their mobility, and it can move successfully on a smooth road. However, the electric wheelchair will have difficult in getting through a barrier if it is not equipped with good suspension system, and it may have a risk of tipping over.
Referring to FIGS. 1 and 2, a conventional electric wheelchair disclosed by U.S. Pat. No. 6,640,916 is shown, at either side of the frame 10 is arranged a connecting member 11 pivoted to a drive rod 12, and the drive wheel 13 is fixed to the drive rod 12. The drive wheels 13 is driven by a motor 14, between the drive rod 12 and the frame 10 is arranged a first spring 15. At the front end of the frame 10 is arranged a pair of cantilevers 16 each have a guide wheel 161, and between the cantilevers 16 and the frame 10 is biased a second spring 17.
In the normal state, the guide wheels 161 are hung without touching the ground, so that when encountering a barrier, the guide wheels 161 will roller over it first, and then the drive wheel can climb up the barrier with its strong driving power.
Although it can overcome a barrier, the conventional wheelchair will consume too much power and cause uncomfortable shock, and the reasons are explained as follows:
First, when encountering a barrier, the drive wheels need to produce a strong driving power for pushing the guide wheel 161 and enabling it to climb up the barrier, however, generating a strong driving power will consume a lot of power.
Second, running on an uneven road, the drive wheels will always bounce up and down without firmly touching the ground, so that the electric wheelchair is unable to move forward stably and smoothly.
Second, when passing a barrier, the cantilevers and the drive rods will bounce up and down under the action of the first and second springs, this cause vibration and make the user feel uncomfortable.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.